Food pH

The pH level of a food is a direct function of the free hydrogen ions present in food. More precisely, pH is defined as the negative log of the hydrogen ion concentration.

Most foods are naturally acidic, with a pH level less than 7. Some of them are basic foods such as egg whites, sweet corn, and some baked goods.

The image is a diagram showing the pH values of foods categorized as high acid and low acid. The pH scale ranges from 0 (strongly acidic) to 14 (strongly basic), with 4.6 as the dividing line between high acid food (below 4.6) and low acid food (above 4.6).

Figure 1. The pH level of some foods. High acids food has a pH value of <4.6. Low acid food has a pH value of >4.6.

Microbes and food pH

The growth of microbes, including yeast, molds, and bacteria, is prevented by very low or high pH. Many foods have a pH low enough to offer some protection towards microbes spoilage, but not low enough to completely inhibit the microbe growth. Yeast and molds can tolerate lower pH than most bacteria.

The pH level of food also determines the time and temperature of the heat treatment it needs.